Generally described, computing devices utilize a communication network, or a series of communication networks, to exchange data. In a common embodiment, data to be exchanged is divided into a series of packets that can be transmitted between a sending computing device and a recipient computing device. In general, each packet can be considered to include two primary components, namely, control information and payload data. The control information corresponds to information utilized by one or more communication networks to deliver the payload data. For example, control information can include source and destination network addresses, error detection codes, and packet sequencing identification, and the like. Typically, control information is found in packet headers and trailers included within the packet and adjacent to the payload data.
In practice, in a packet-switched communication network, packets are transmitted between multiple physical networks, or sub-networks. Generally, the physical networks include a number of hardware devices that receive packets from a source network component and forward the packet to a recipient network component. The packet routing hardware devices are typically referred to as routers. Generally described, routers can operate with two primary functions or planes. The first function corresponds to a control plane, in which the router learns the set of outgoing interfaces that are most appropriate for forwarding received packets to specific destinations. The second function is a forwarding plane, in which the router sends the received packet to an outbound interface.
For ease of administration, routers on large internetworks such as the Internet are typically grouped into autonomous systems (ASes) that are independently controlled by different organizations and companies. Interior routing protocols such as RIP and OSPF are used to communicate routing information between routers within an autonomous system while exterior routing protocols, such as BGP, communicates routing information between ASes.
Generally, the details of what happens within an AS are hidden from other ASes, providing the AS administrator with independent control of the AS, including the selection of an interior routing protocol from a variety of different interior routing protocols. In contrast, in order to reliably connect ASes together, different ASes run compatible exterior routing protocols.